I mean, he's got all sorts of legendaries on Pokémon X such as Shiny Giratina, shiny Charizard and Thundurus. He also got Zekrom, Articuno, Moltres and Zapdos. I really would like to know how.
Serebii's Event Database has a complete list of every Event Pokémon, in most countries. Also, I'm sure some of you friend's uncle's Shinies are naturally-occuring.
Might I just add that your friend probably has the coolest uncle ever.